Funktionelle Analyse und Dynamik der regulatorischen Schaltkreise des TEA-Transkriptionsfaktors Tec1 in Saccharomyces cerevisiae

Haploid cells of the baker’s yeast Saccharomyces cerevisiae can execute the two developmental programs mating and adhesive growth depending on environmental influences. The highly conserved Fus3/Kss1-MAPK module is involved in this regulation and controls the two transcription factors Tec1 and Ste12. During mating, the adhesion-specific Tec1 is degraded to prevent an undesired activation of target genes of adhesion during mating. However, the promoter of TEC1 contains, amongst Tec1-specific binding sites (TCS-elements; TEA/ATTS consensus sequence) also potential binding sites for Ste12 (PREs; pheromone response elements) suggesting that the TEC1-promoter is directly bound by Ste12 and the TEC1-transcription is induced during mating contrary to the expectations. Therefore, the transcriptional and translational regulation of Tec1 particularly by Ste12 was investigated in the work presented here. First, the role of the autoregulation and the regulation by Ste12 in control of TEC1-expression during different developmental programs was analyzed and it was determined, if exclusive environmental signals are selectively processed by a specific regulatory circuit. Here it could be shown that the expression of TEC1 during vegetative growth and mating is mainly controlled by Ste12 via the PREs whereas the TCS-elements are not required for an efficient transcription. Moreover, it could be shown that the TEC1-expression and protein stability is influenced by different nutritional signals. A lack of glucose for example led to increased TEC1-transcript and Tec1-protein levels, whereas nitrogen deprivation seemed to only slightly induce TEC1-transcription but Tec1-protein stability is negatively influenced. Here it was also shown that the control by nutrients is probably not processed by the TCS- or PRE-mediated regulatory circuit but by so far unknown mechanisms. In the second part of this study it could be shown that the 3’ untranslated region (UTR) of TEC1 is probably important for control of TEC1-translation by the RNA-binding protein Mpt5. The third part of this work describes the successful uncoupling of TEC1-expression from Ste12-mediated control by synthetic doxycycline-mediated control of transcription. It was shown that the control of TEC1-expression by Ste12 can be replaced by a single binding site for a doxycycline-regulated activator. Additionally, it was found that the promoter of the human cytomegalovirus is presumably not efficiently activated in S. cerevisiae to produce a sufficient amount of doxycycline-regulated activator which can subsequently activate TEC1-expression.